What is an Air Handler?

An air handler is an often overlooked, yet essential part of your central heating and cooling system. An air handler, or air handling unit (often abbreviated to AHU), is a device used to condition and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system.

An air handler is usually a large metal box containing a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers. Depending on the design and system type, air handlers also can hold compressors, filters, humidifiers, dampers and control units (boards).

Air handlers usually connect to ductwork that distributes the conditioned air through the building and returns it to the AHU. Sometimes AHUs discharge (supply) and admit (return) air directly to and from the space served without ductwork.

Air Handler's Job

Air handlers are responsible for conditioning the air of a building to the right temperature, humidity and air purity level. Most systems work like this:

A gas such as freon is compressed into liquid form. This process has the byproduct of heat. The liquid travels through a valve to an area where pressure is not as high, and it converts back into a gas, taking heat out of the air. This makes the pipes cooler. The fan blows the cold or warm air from this process out into the room.

Types of Handlers

There are three main types of air handlers. Those in HVAC systems are mainly designed to keep moisture levels under control and to keep temperature comfortable.

Air filter handlers, such as air purifiers, filter the air to remove allergens, pollutants and other pathogens.

The last type, hot water, is different from the other types in that it requires a condenser or furnace, as well as a water heater or boiler. In general, air handlers can be categorized as home or commercial, as well.